Without limiting the scope of the invention, its background is described in connection with polymeric biocides. To contain the spread of infectious pathogens, materials that can effectively inactivate microorganisms upon contact have attracted considerable interest. One common method in the preparation of antimicrobial materials is to directly add antimicrobial additives into materials during processing.
Many materials (e.g., polymers, fibers, medical devices prone to biofilms) are remarkably difficult to treat with antimicrobials, which may be readily inactivated or fail to penetrate into the materials. In addition, bacteria within such materials have increased resistance to antimicrobial compounds, even though these same bacteria are sensitive to these agents if grown under planktonic conditions. Furthermore, bacteria express new, and sometimes more virulent phenotypes when grown within different materials. The growth conditions are quite different particularly in the depths of biofilms, where nutrients and oxygen are usually limited, and waste products from neighbors can be toxic. In short, bacteria found at the bottom of the materials can look and act different from bacteria located at the surface. The medical, industrial and environmental fields already see such problems, e.g., bacteria resistant to both immunological and non-specific defense mechanisms of the body.
Microorganisms have strong abilities to survive on ordinary materials and studies have shown that some species can stay alive for as long as 90 days. The contaminated materials serve as major sources of infectious diseases. Therefore, the introduction of biocidal functions into a target material can be an effective method to inactivate the microbes and thus reduce infection rates. Although many technologies have attempted this process, successful examples in this field are still limited.
U.S. Pat. No. 6,762,225, issued to Malik, et al., for light stabilizer composition and teaches a light stabilizer composition obtainable by mixing a polymer with at least one polyalkylpiperidine and at least one free radical generator and melt-blending of that mixture at a temperature above the melting point of the polymer and above the decomposition temperature of the free radical generator and at shear conditions sufficient to blend the components. The light stabilizers of this patent provide a method for enhancing the light stability of polymers, preferably polyolefins.
U.S. Pat. No. 6,670,412, issued to Erderly, et al., for a method of melt processing amine containing polyethylenes and teaches a processed linear polyethylene containing an amine additive shown to exhibit improved processability through the addition of certain surfactants. The amine compounds are generally one or more hindered amine light stabilizers, amine antistats, amine antioxidants or amine based UV inhibitors. Among the melt processing parameters improved are reduced head pressure, reduced torque, reduced motor load, reduced or eliminated melt fracture, or combinations of these parameters.
The foregoing problems have been recognized for many years and while numerous solutions have been proposed, none of them adequately addresses all of the problems.